Surface analysis on industrial surfaces — now comparable

Interlaboratory test analysis with GDOS and SNMS were conducted by 8 laboratories on certified standard specimens and on a technical steel sheet to determine the elemental concentrations, possible changes of its surface composition due to the manufacturing process and to establish the repeatabilities and reproducibilities under depth profile conditions.     

Integrating methods for the analysis of oxide scales on high-temperature alloys using GDOS and EPMA

Summary The oxidation of Ni-based alloys leads to multiphase oxide scales with an inhomogeneous microstructure. By introducing an integrating method for EPMA it was possible to find a common basis with GDOS depth profiles for the chemical characterization of such layers. At first it was necessary to quantify the GDOS intensity profiles; thus the comparison of relative mass fractions supplied by both methods was successful. Generally it was found a substantial agreement also with quantitative SNMS profiles.     

Influence of surface structure on surface analytical statements

The influence of surface structure of technical materials on results and statements of surface analytical methods has been investigated. Especially surface roughness as a typical property of rolled products has been observed. For this purpose samples of steel (technical surface, roughness up to 5 m) and silicon wafers (polished surface) have been analyzed by SNMS and GDOS in order to get information about changes of the surface roughness as function of the sputtering time and their influence on the statements about the depth profiles obtained.     

Quantitative depth-profiling with GDOS: application to ZnNi-electrogalvanized steel sheets

Summary Studies are made on quantitative GDOS depth profile analysis for ZnNi-coatings. Relative and absolute depth resolution on the interface ZnNi-coating/steel substrate were evaluated in a thickness range of 0.5 to 5 m using two different anode tube diameters. For quantification, an improved approach of the model of constant emission yield was established. The results are demonstrated on ZnNi-electrodeposits with different coating thickness and chemical content.     

Calibration standards for composition-depth profiles of non-stoichiometric titanium nitride coatings

Five different TiN_x coatings have been deposited on steel substrates by reactive magnetron sputtering. A quantitative analysis was carried out in two ways. The coatings were initially analysed by GDOS and after removing the coatings from the substrates and digesting the TiN_x powder, nitrogen was quantified by the Kjeldahl technique and titanium by AAS. A comparison of the results shows that AAS and Kjeldahl results correlate very well, whereas GDOS results deviate from these two methods systematically.     

Determination of thickness distribution and composition of thin coatings by EPMA: Application in the field of steel sheet production

A new method for the investigation of surface coatings by EPMA is presented. It is based on a physical model which takes into account the X-ray intensity depth distribution, the absorption and the electron backscattering effects at the interface between film and substrate. When combined with the concentration mapping (CM) technique, a two-dimensional film thickness distribution and the film composition can be determined simultaneously. Only bulk standards are required for this method.With some examples in the field of steel sheet production and electrogalvanizing the versatility of the method as well as its high sensitivity are pointed out. Particularly important for practical work is the applicability to almost any combinations of film and substrate materials as well as the wide thickness range from almost the total X-ray emergence depth down to the monolayer range.Dedicated to Professor Günther Tölg on the occasion of his 60th birthday     

Grazing-exit X-ray spectrometry for surface and thin-film analyses.

Electron-probe x-ray micro analysis (EPMA) and particle-induced x-ray emission analysis (PIXE) were performed under grazing-exit conditions. To control the exit angle (take-off angle), a new sample holder having a stepping motor was developed for grazing-exit EPMA. A carefully polished surface of a stainless-steal sample was measured. The surface of stainless steel is normally covered with a thin native oxide layer. The intensity ratio of Cr K(alpha) to Fe K(alpha) increases significantly at the grazing angle, becoming about 5-times larger at 0.2 degrees than at 40 degrees. This result indicates that grazing-exit EPMA is useful for surface analysis. In addition, a new PIXE equipment was developed for grazing-exit x-ray measurements. The sample is fixed and the x-ray detector is moved by applying a linear stage. Preliminary experimental results of grazing-exit PIXE are also shown.     

Analysis of nitrogen-influenced surface near zones of ferrous materials by glow discharge spectroscopy (GDOS)

Glow discharge spectroscopy (GDOS) will be shown to be a quick, informative and simple method for quantitative depth profile analysis of elements of nitrided layers well suited for their quality control. By systematic variation of all glow discharge determining parameters it is possible to get an excellent depth resolution in the order of sub-m corresponding to a comparatively large analytical activated area (50 mm²). In this paper the behaviour of a number of important parameters related to sputtering of the activated area will be discussed. Some quantitative GDOS depth profiles of carbon and nitrogen of pure iron samples nitrided by different procedures will be shown as examples for application.     

Influence of the topography of zinc coated sheet on the results of electron probe microanalysis

As far as possible, electron probe microanalyses (EPMA) must be carried out on optimally smooth surfaces. When analyzing technical surfaces with a roughness resulting from the rolling or coating process, EPMA results are biased, which has consequences especially when determining element mass layer in the detection limit area. This effect was tested and a corrective process was developed on electrolytically galvanized and hot-dip galvanized steel sheet of varying roughness.     

Eignung von Tiefenprofilanalysen zur Charakterisierung von Oxidschichten an Hochtemperaturlegierungen

Summary The characterization of oxide scales by their composition and structure is necessary in order to predict their protective behaviour for the high temperature alloys in various corrosive media. For this purpose information obtained by classical methods, such as metallography, X-ray diffraction and microprobe analysis can be supplemented by depth profiles determined by various spectroscopical methods.In this paper, HASTELLOY X und INCONEL 617 were oxidized for relatively short times in two different atmospheres. Depth profiles were determined by GDOS (Glow Discharge Optical Spectroscopy), SNMS (Secondary Neutral Mass Spectrometry) and SIMS (Secondary Ion Mass Spectrometry).The measured profiles were compared with the results of non-destructive X-ray diffraction analysis to characterize the scales and the oxide-metal interface.     

Characterization of metallic and ceramic high-temperature materials for energy systems

For the development of metallic and ceramic high temperature materials used, for example, in heat exchanger components, in turbine blades for stationary gas turbines, in ceramic industrial products and fusion reactor components, modern physico-chemical characterization methods are required. The formation stability of naturally formed protective scales is of prime importance in the successful application of metallic materials at high temperatures in aggressive atmospheres. For the characterization and investigation of the growth mechanisms of such surface scales, the main emphasis is placed on such modern spectroscopical methods as SIMS, SNMS, GDOS, EPMA and RBS. The morphology and composition of oxide scales have been investigated by imaging and diffraction techniques. The thermal and mechanical damage behaviour of high-temperature materials for application in fusion reactor components is of importance. Damage behaviour has been simulated by electron beam and laser irradiation experiments, especially by means of in situ techniques in a scanning electron microscope. By such techniques the material erosion, crack formation and crack propagation were studied for ceramic high temperature materials as a function of load parameters. The erosion and the crack formation processes are superim-posed by a redeposition of vaporized material and by thermally activated creep of the binder phases. The application potential for all methods discussed is outlined and available results are presented.     

New approach to online monitoring of the Al depth profile of the hot-dip galvanised sheet steel using LIBS

In this study a new approach to the online monitoring of the Al depth profile of hot-dip galvanised sheet steel is presented, based on laser-induced breakdown spectroscopy (LIBS). The coating composition is measured by irradiating the traversing sheet steel with a series of single laser bursts, each at a different sheet steel position. An ablation depth in the same range as the coating thickness (about 10 μm) is achieved by applying a Nd:YAG laser at 1064 nm in collinear double-pulse and triple-pulse mode. The ablation depth is controlled by adjusting the burst energy with an external electro-optical attenuator. A fingerprint of the depth profile is gained by measuring the LIBS signals from zinc, aluminium and iron as a function of the burst energy, and by post-processing the data obtained. Up to three depths can be sampled simultaneously with a single laser burst by measuring the LIBS signals after each pulse within the laser burst. A concept for continuously monitoring the Al depth profile during the galvanising process is presented and applied to different hot-dip galvanised coatings. The method was tested on rotating sheet steel disks moving at a speed of up to 1 m/s. The potential and limitations of the new method are discussed.     

L'analyse des surfaces métalliques par spectrométrie d'émission à décharge luminescente

For several years, glow discharge spectrometry has been used at IRSID to characterize the surface layer composition of steel products, in particular, steel sheets. We recall in this communication the basic principle of the Grimm emission source and we discuss the influence of different parameters on the depth resolution of this technique.Some examples are then presented: Control of the surface cleanliness of pure iron (polished sample), study of passivation films formed on a ferritic stainless steel, and depth distribution of carbon on a mild steel sheet. These examples, taken among many others, show the usefulness of this technique for analysing films of varying thickness in the nanometer to micrometer range covering most of the elements which are important for steelmaking.     

Heterogeneous element distribution: a contribution to quantitative GDOS depth analysis

Summary The apparent enrichment of Cu, Mg, Mn and Si on the surface of Al cast-alloys, as observed by means of glow discharge optical emission spectrometry (GDOS), could be attributed to the heterogeneous distribution of the alloying elements. The samples under investigation were spectrochemical standards and hence assumed to be homogeneous. Different metallurgical phases were identified which induced selective sputtering. The findings point out that quantitative results obtained by GDOS in-depth analysis can be misleading and should be confirmed by other techniques such as Auger Electron Spectrometry and Energy Dispersive X-ray Spectrometry, which are free from sputter effects.     

Zur Bestimmung der Zusammensetzung und Homogenit?t reaktiv gesputterter SiNx-Schichten

Summary Thin SiN_x-layers are to be used for joining Si₃N₄ ceramics. For the characterization of such layers produced by reactive sputtering using a RF magnetron cathode, the chemical composition requires determination. Layers were therefore sputtered under various sputtering conditions onto stainless steel, graphite and silicon substrates and then analyzed using three different methods: Glow Discharge Optical Spectrometry (GDOS), Electron Microprobe Analysis (EMPA) and Rutherford-Backscattering (RBS).     

Combined EPMA and AES depth profiling of a multilayer Ti-Al-O-N coating

In order to compare thin-film electron probe microanalysis (EPMA) and Auger electron spectroscopy (AES) regarding reliability in quantifying chemical compositions of Ti-Al-O-N coatings with depth, a multilayer was prepared on a silicon wafer by using reactive ionized cluster beam deposition technique. Within a total thickness of about 25 nm the composition of the multilayer varied step by step from Ti-Al-O-N at the bottom to Al-O at the top. AES and, as an innovation, EPMA crater edge profiling was applied to measure the composition with depth. For quantification special thin-film EPMA techniques based on Monte Carlo simulations were applied. The chemical binding states of Al and Ti with depth were analysed using a high resolution energy analyser (MAC 3) for the AES investigations working in the direct mode. According to the deposition procedure the concentration profiles of the components varied with depth for both AES and EPMA measurements. AES provided a better depth resolution than EPMA. To get a true calibration of the depth scale an in-situ measurement method like an optical interferometry will be required. Assuming that the relative sensitivity factors are available AES depth profiling delivers concentration profiles with good accuracy. The new EPMA application provided quantitative depth profiles concerning concentration and coverage. For EPMA crater edge profiling the coating needs to be deposited on a foreign substrate because depth distributions of elements being present in both the layer and the substrate cannot be resolved.The combination of AES-depth profiling with EPMA crater edge profiling techniques is a powerful tool to analyse heterostructures quantitatively.     

Process analysis in steelmaking and steel processing

Because of the importance of steel or the element iron for the prosperity of the world it has been of great interest to look at the mutual relations between the modern metallurgical engineering and the state of process analysis under scientific and economical aspects. Process analysis comprises discontinuous and continuous procedures whereas more and more on-line techniques are required and of increasing importance. The paper illustrates the state of the art at the different metallurgical stages beginning with the blast furnace process and the steelmaking process routes. It will be shown that the highly sophisticated, computer-aided spectrometric and electrochemical methods applied play an essential role for process control and optimization. A survey is given about the research projects for direct analysis of melts, i.e. analysis without any sampling. Steel sheet production by rolling and annealing need analytical investigations as well as the metallic and organic coating processes. Of main interest are all questions related to surface properties. In this field the analyst has to face problems of inorganic and organic nature. It can be seen that coating is the last link of a process chain of continuous treatments in steel processing. Finally, the relations between material development and material analysis will be explained by example. Summarizing it will be stated that the modern, quality assured steelmaking and steel processing need the urgent assistance of process analysis for optimization. Process analysis and material analysis are of increasing importance for the scientific, technical, and economic progress.     

Quantification of SNMS investigations of coated materials

Summary In recent years surface analysis has become essential for materials analysis accompanying the production of flat steel products, especially of coated materials. Secondary neutral mass spectrometry (SNMS) can be looked upon as a new tool for further approach with many advantages compared with other spectrometrical methods. Our investigations started with the determination of detection limits of some important accompanying elements in steel and tests on the applicability of SNMS for bulk analysis. Sensitivity factors were determined as a prerequisite for the quantification of SNMS signals. The application of SNMS for solving industrial problems is demonstrated by some examples from the production of coated materials like galvanised sheet.

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Versuche zur quantitativen SNMS beschichteter Werkstoffe

     

Advanced surface techniques for characterization of Cu-base artefacts

Patinae on Cu-base alloys have been characterized by means of GDOS, SEM, XRD and AFM. The effect of a protective coating was tested in aggressive artificial solutions. Patinae and the bulk of several metal Punic objects were also examined. The GDOS results combined with SEM capabilities allow exhaustive investigation of composition, element distribution and microstructure of modified surface in modern bronzes exposed to accelerated ageing tests as well as in ancient bronzes. The SEM data of the patina thickness agree with the GDOS data. The XRD and SEM investigations allow an exhaustive characterization of corrosion products. Corrosion growth in its early stages determines the effectiveness of the patina's protective role and the AFM is a promising technique for investigating this.